Barnsbury Square, London

The stunning new build development of apartments in London required a below ground waterproofing solution.

The Challenge

Barnsbury Square is a stunning development of 10 light and spacious lateral apartments arranged around a landscaped courtyard in the heart of the Barnsbury conservation area.

Cast Contracting Ltd (CCL) were commissioned by award winning contractor Gilbert Ash to supply and install comprehensive structural waterproofing solutions to the underground car park, plant rooms, cycle storage and general storage areas within the complex.

The residential development was required to be waterproofed to a Grade 3 habitable environment in accordance with BS 8102:2009 (Protection of below ground structures from the ground).

The Solution

CCL recommended the installation of RIW Structureseal pre-applied sodium bentonite system under the entire basement ground-bearing RC slabs. RIW R20 Cavity Drain membrane was applied to the steel-sheet piled retaining walls to each of the basement levels prior to a third party installing internal blockwork wall lining. RIW Aquachannel was then installed to the recessed channels in the lower basement and the suspended concrete slabs, with the aim of collecting water and diverting it to the pumped sump systems. John Newton twin sump pump systems, consisting of two Titan NP400 pumps, battery back- up and high-level water alarms, were fitted within the Newton Titan Pro sump chamber.

RIW Cementflex waterproof coating was then applied to the inside face of the channel to the top of the suspended basement slabs, to provide a waterproof lining to prevent water from travelling horizontally across upper basement slabs.

RIW R20 Cavity Drain membrane was installed across the entire ground bearing basement slab prior to the installation of screed and finishes. Finally, RIW Cementseal cementitious waterproof coating was installed to the inside face of concrete walls and floors of the passenger lift-pits and attenuation tanks to complete the waterproofing works.

Client Testimonial

“CCL’s specialist team delivered a comprehensive waterproofing solution at Barnsbury Square that met strict deadlines. Their pro-active approach ensured that any challenges on-site such as fixing the RIW R20 Cavity drain membrane vertically to steel sheet piling without fully penetrating & compromising it’s waterproofing integrity, were overcome practically, demonstrating their technical understanding of the products and installation processes.”

Emmett Holmes, Project Manager, Gilbert Ash

Products Specified

  • RIW Structureseal
  • RIW R20 Cavity Drain
  • RIW Aquachannel
  • RIW Cementflex / RIW Cementseal
  • RIW Overtape
  • RIW Toughseal
  • Newton Titan Pro Sump Chambers
  • Newton Titan NP400 pumps
  • Newton High level water alarm
  • Newton Victron Inverter battery back-up system

Design | Supply | Installation

Cast Contracting Ltd (CCL) is the UK’s leading specialist in Design and Installation of all Waterproofing, Tanking and Ground Gas Systems across the United Kingdom. CCL prides itself on offering the highest level of service throughout the Design, Planning, and Installation process.

Structural Waterproofing & Ground Gas Solutions

CCL’s in-house design team can offer a comprehensive proposal for all scenarios in line with BS:8102 and BS:8485.

CCL Guarantees

One of the most comprehensive Guarantees across the industry, taking full project ownership.


Cast Contracting Limited is one of the longest standing industry specialists. As it is now part of the CCL Group of Companies, Cast Contracting Ltd has the additional stability and support with over sixty employees across the Group.

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